# When to turn on heater?

#### browerjs

##### Member
Just had my pool installed over the fall and it will be opened today. I'm in Ohio, and was wondering when the best time would be to turn on my heater. I have a Hayward HeatPro Heat PumpHP21254T. I don't want to get killed with electric bills, and we are about ready to go through a bit of a cold spell.

#### ajw22

Gold Supporter
TFP Guide
A heat pump generates heat slowly do you need to anticipate when you will have nice weather and want to swim.

Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source. Yiu can out in your electrical cost and get an idea of cost to run your HP by month.

#### browerjs

##### Member
A heat pump generates heat slowly do you need to anticipate when you will have nice weather and want to swim.

Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source. Yiu can out in your electrical cost and get an idea of cost to run your HP by month.
I thought I read that it needed to be at least 50 degrees for an electric heater would be efficient. The lows are never going to get above 50, so I wasn't sure. So is the idea I just turn it on right away and then turn it off once the air temp is over 84 consistently? And then turn it back on in Sept/Oct?

Sorry, I'm a noob

#### ajw22

Gold Supporter
TFP Guide
I thought I read that it needed to be at least 50 degrees for an electric heater would be efficient. The lows are never going to get above 50, so I wasn't sure. So is the idea I just turn it on right away and then turn it off once the air temp is over 84 consistently? And then turn it back on in Sept/Oct?

Sorry, I'm a noob
Even if on your HP will not generate heat when the air temp is below 50. You can leave it on and your pump running and it will give you heat when it can. You need to see if you get sufficient heat during the day to get your pool to your desired temperature.

Do you have a cover? It will help reduce heat loss at night and reduce how much the HP needs to run to maintain the desired pool temperature.

You turn your HP on or off based on if you have the desired pool water temperature, not air temperature.

#### browerjs

##### Member
Even if on your HP will not generate heat when the air temp is below 50. You can leave it on and your pump running and it will give you heat when it can. You need to see if you get sufficient heat during the day to get your pool to your desired temperature.

Do you have a cover? It will help reduce heat loss at night and reduce how much the HP needs to run to maintain the desired pool temperature.

You turn your HP on or off based on if you have the desired pool water temperature, not air temperature.
So it won't run if the air temp is too low? I just want to make sure I'm not spending money to heat if it's not going to work because the air temp is too low.

#### ajw22

Gold Supporter
TFP Guide
So it won't run if the air temp is too low? I just want to make sure I'm not spending money to heat if it's not going to work because the air temp is too low.
Correct.

But you are wasting money running the HP when it cannot get your water to the desired temperature during the day.

#### browerjs

##### Member
Correct.

But you are wasting money running the HP when it cannot get your water to the desired temperature during the day.
So in other words, just turn it on, set it, and forget it. And keep the solar cover on over night.

#### ajw22

Gold Supporter
TFP Guide
So in other words, just turn it on, set it, and forget it. And keep the solar cover on over night.
Yes, if you want a swimable pool at your desired water temperature.

#### Randrx2

Bronze Supporter
Heat pumps are getting better and better at pulling heat out of “cold” air. Older units used to only be able to work when temps were in the 50s. Newer heat pumps can work down into the 40s.

It looks like your unit is set up so that if the temp is too low outside, it will shutoff. It also states a range of this shutoff temp at 45-55F.

I would wait, because it is WAY to cold for me. But, I’m from Florida. Less than 60 air temp is cold to me! Water temp for us needs to be greater than 85F to be comfortable.

But seriously, most manufacturers tend to use the 55F temp as the low point at which the heat pump works best or outputs their advertised heat values.

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#### revitup

Bronze Supporter
I have a similar Hayward HeatPro (hp31204t). It won't kick on until about 53F ambient air temp. Displays a "LP" code below that temp. It can be fooled by putting the temp sensor in the sun but it won't add much heat to the pool, it'll just run all day. Once your ambient temps reach a minimum reasonable swimming level, mid-70s in my opinion, it'll produce some heat. Takes about an hour to get 1 degree rise in my 8500 gal pool. I start my pump about 6AM and I'm up to 85 degrees by noon or so.